Chromosome Abnormalities and Viability of Vitrified Eight-Cell Mouse Embryos at Presence of Two Different Cryoprotectants at Different Storage Durations

OBJECTIVE Experiments were conducted to find the differences between post-thaw viability and chromosome aberrations in eight-cell mouse embryos at presence of dimethyl sulfoxide (DMSO) and 1, 2-propanediol (PROH) as croprotectants in different storage durations. MATERIALS AND METHODS In this case-control study, a total number of 720 mouse embryos from about 250 NMRI mice were vitrified with 30% PROH or DMSO; each diluted with a solution containing 30% ficol plus 0.5 M sucrose. Embryos were exposed to the solutions for 0.5 minute at 25℃ followed by cooling in liquid nitrogen, then after appropriate storage duration, they were rapidly warmed. Besides, there were 100 mouse embryos for each cryoprotectant group (totally 200 embryos) as control. Embryo survival was assessed by in vitro development, and chromosome abnormalities were analyzed by Giemsa staining. RESULTS The proportion of mitotic abnormalities in PROH/DMSO vitrified embryos was significantly higher than unfrozen control group. This was confirmed also by a reduced viability of the embryos as judged by a culture at the blastocyst stage (p<0.05 in all test groups). CONCLUSION It can be deduced that long term cryopreservation may result in chromosomal abnormalities and/or low viability.